Method of electrolysis



Patented Jan. 5, 1932 I UNITED STATES URIJYN C. 'I'AIN'IfOIN', OF EAST ST. LOUIS, ILLINOIS mmnon or n'mcrnonysrs No Drawing. Application filed May lS,

This invention relates to improvements in methods of electrolysis, and especially to a method of preventing liberation of spray or acidmist from-the surface of the electrolyte in an electrolytic cell.

In many electrolytic operations, more especially those involving the electro-deposition of metals, gases are evolved at either the anode or the cathode, or both. 'The small bubbles of gas, on reaching the surface of the liquid, burst, and throw minute droplets of the electrolyte into the air, forming a spray or mist. Where the electrolyte is corrosive, as in the production of electrolytic zinc and copper, and in chromium plating, this spray becomes a serious nuisance. It causes rapid deterioration of the cell equipment, copper conductors, and buildings. It constitutes a definite menace to the health of the workmen. In the case of electrolytic zinc plants it is usually necessary for the workmen in the cell room to wear respirators or gas masks and even with these precautions their active working hours mustbe curtailed. Attempts have been made to control the trouble by the use of floating layers of oil but the oil always finds its way to the cathode surface and in most cases spoils the character of the metal deposit, usually making it spongy andnonadherent.

According to the present invention, this nuisance may be eliminated by the addition to the cells of very small amounts of certain substances which afi'ectthe surface tension of the electrolyte. Preferably'these substances are of such a kind as to produce a foam or froth on the surface, thereby confining the spray which would otherwise be given ofi by the bursting bubbles. Any substance or combination of substances may be employed which will roduce this result without adversely afiectmg the electrolytic operation. I have found it frequently of advantage to use such materials as will, in addition to modifying the surface tension, give also a finely divided solid precipitate which will float to the surface and make the froth more permanent and durable by virtue of the well-known property of finely divided solids to form continuous films at a liquid-gas interface. A substance which I 1929. Serial No. 362,874.

have found of special value for this purpose consists of. a mixture of cresols technically known as cresylic acid, derived from the destructive distillation of organic matter. Other derivatives of wood and coal tar are effective such as xylenol and creosote. Another su stance which may be used consists of rubber latex or natural juice of the rubber tree, stabilized with suitable addition agents. I have found certain glucosides, more especially .saponin, to be efficacious in many cases, and it is understood that I do not wish to limit myself to the use of specific reagents. The number of possible organic compounds is practically unlimited and it. would be impossible to investi ate each one from the standpoint of its suitability for this purpose. The reagents specifically mentioned are those which, in the course of an extensive research, have proved of definite value.

In illustration of the mode of carrying this invention into effect, I will describe its application to the electrolytic production of zinc from sulphate solutions. An emulsion of cresylic acid is prepared by a violent agitation with water containing gum arabic. Convenient proportions are one part of oresylic acid. to parts of a two per cent solution of gum arabic. This emulsion is added to the cells either by mixing with the electrolyte or by spreading on the surface. The emulsion is. normally added continuously or at short intervals in such amount that about one pound of cresylic acid is put into the electrolyte for each ton of metallic zinc deposit at the cathode. This represents a proportion of about one part of cresylic acid to ten thousand of electrolyte. Any other proportions may be used according to the intensity of the effect which it is desired to obtain.

Better results are obtained if there is present in the electrolyte a small quantity of silicic acid, as a more stable froth is obtained in the presence of silicic acid.

Rubber latex may be added in a similar way, though in this case the addition of the gum arabic is not usually necessary. Saponin may be dissolved in water and the solution added as required to prevent spray formation. One part of saponin to thirt ghousand of electrolyte will ordinarily su It will be found that the immediate efiect of the procedure above mentioned will be the formation of a froth on the surface of the solution which effectively restrains formation of the acid mist which would otherwise be formed.

Having thus described the nature of my' invention, what I claim and desire to secure by Letters Patent is:

1. The method of preventing liberation of spray or mist from the surface of an electro lyte in an electrolytic cell evolving gas which consists in adding a frothing agent to the electrolyte so as to form a layer of stable froth on the surface of an electrolyte occluding the gas.

2. The method of preventing liberation of spray or mist from the surface of an electrolyte in an active electrolytic cell which consists in adding a tar of the class of creosote, xylenol, and cresol to the electrolyte so as to form a layer of froth on the surface of the electrolyte.

3. The method of preventing liberation of spray or mist from the surface of an electrolyte in an active electrolytic cell which consists in adding cresylic acid to the electrolyte so as to form a layer of froth on the surface of the electrolyte.

4. The method of preventing liberation of spray or mist from the surface of an electrolyte in an active electrolytic cell which consists in adding a mixturaof cresylic acid and silicic acid to the electrolyte so as to form a layer of froth on the surface of the electroyte.

5. The method of preventing liberation of spray or mist from the surface of an electrolyte in an active electrolytic cell which consists in adding silicic acid to the electrolyte, and an organic compound capable of combining with the silicic acid so as to form a froth on the electrolyte.

URLYN C. TAINTON. 

